see http://clang.llvm.org/extra/clang-tidy/

`add_format` now only takes one argument: a directory that is used
the base dir for recursive globbing files into clang-format
Usages of the macros are adjusted accordingly. It's still possible to
use it multiple times in a project, if one for whatever reason
does not wnat to throw it at the source root. Only one `format`
target will be generated either way, with one subtarget per
`add_format` invocation.

this closes #10

clang format discovery is improved a lot by using cmake
builtins, allowing us to very easily target a specific
version only.

This is one half of #10

instead default to activate dune-common's

also fix default max for intel's MIC platform

For some reason cmake errored out if Likwid was not found on that
platform.

refs #30

this builds and runs tests w/o ctest first. Errors here will and should
fail our travis build as such. Afterwards ctest is run again on a
cleaned build dir. This should replicate results and submit those to
cdash, while enabling us not to have the travis build fail due to ctest
itself failing.

GridUtils now default to YaspGrid, which is now also the only
grid implementation guaranteed to be availabe for testing
if dune-grid is present

This reverts commit ba71a7857d78f85ff258834f7820928c253102af
since the update required cmake stuff in common (>=2.4)